Students create a sketch in which a dramatic animation shows how the sum of the areas of two squares is equal to the area of the third square. The link to the tool itself is to a zip file that contains both the sample sketch (designed to help teachers understand how the activity should work) and a pdf file of the corresponding activity.

The combined sketch and pdf activity file are also available in .sit format. This is a free sample activity from Pythagoras Plugged In: Proofs and Problems for the Geometer's Sketchpad.